On Wed, Feb 18, 2004 at 09:37:42PM -0000, Jim Jarvis wrote:
>
> Al,
>
> I own a 3 el. SteppIR. Went through exactly the selection process
> you're experiencing now. Some thoughts:
>
> * Fixed element spacing can be accomodated, to some degree, by
> element tuning. The antenna gives you a reasonable half-power
> beam width, and good f/b on all frequencies, 20-10. I doubt
> that any beam on similar boom length will beat the SteppIR
>
> * A 3 element monobander...or 3-3 element monobanders on a common boom,
> like the current crop of 'tribanders', will likely equal the
> SteppIR. EXCEPT that the vswr bandwidth may not be where you
> want them, and may require iterative tweaking to get them where you
> want them. With the SteppIR, you just put it up and tune it from
> inside.
>
> * Stepper motors are highly reliable. Ask fluid motion about crash
> parts, if a tree attacks the antenna. you'll find they're reasonable.
>
> * They have no 30/40m solution, except for the bigIR vertical. I've been
> thinking of a CC 40, with 2 30m elements inside it, on the same
> boom. SteppIR appears to be limited by the size of the molded motor
> housing. They can't accomodate bigger spools without tooling a new
> housing. I'd love it if they did. 2 els on a 24' boom would be ideal.
>
I can think of a number of possible ways to accomplish this:
1. Two BigIRs back to back for each element. This might get expensive
as it would require 2 stepper motors on each element.
2. A fixed element (either aluminum or fiberglass with copper tape)
with a stepper motor and variable-length tape at the ends to tune from
7 - 10.1 MHz. The control wires could run inside the tubing. With the
larger spacing required for 30/40, it wouldn't be practical to use it
over 40-6 meters anyway.
3. A single stepper motor, as in the current SteppIR, but with
elements which only partially retract, allowing the spool to fit the
current housing.
Bob, N7XY
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